The present invention relates to display devices for broadcast receivers with a plasma discharge display panel, computer instruments and the like, including the display panel itself, and light sources having a fluorescent lamp such as the back light of a liquid crystal display or the like.
In recent years, display devices of broadcast receivers, computer instruments and the like using a plasma display panel (hereinafter, referred to as PDP) which is a plasma discharge display panel have come to be mass-produced.
A PDP makes a color display by emitting light from a phosphor placed in a discharge space by using a short-wavelength ultraviolet light generated in the negative glow region in a micro discharge space containing a rare gas (when xenon is used as the rare gas, its resonance line is at 147 nm or 172 nm) as an excitation source.
In a PDP, a resonance line of a rare gas of which the emission wavelength is shorter than that of mercury vapor resonance line (253.7 nm) or the like is used as the excitation source of the phosphor, and the lower limit wavelength thereof is the resonance line of helium (58.4 nm).
The structure of the gas discharge cell of a PDP is, for example, as shown in xe2x80x9cTechniques and Materials of Color PDP/published by C.M.C. K.K.xe2x80x9d, and the typical structure is shown in FIG. 7.
FIG. 7 is an exploded perspective view illustrating the structure of a general surface discharge type color plasma display (PDP), wherein a rear glass substrate 20 on which a red (R) phosphor layer 24, a green (G) phosphor layer 25 and a blue (B) phosphor layer 26 are formed and a front glass substrate 10 made of a glass substrate are laminated to each other to form an integrated body.
The front glass substrate 10 has a pair of display electrodes 11 and 12 formed on a surface confronting the rear substrate 20 in parallel with each other with a constant distance. The display electrodes 11 and 12 are transparent electrodes. Opaque bus electrodes 13 and 14 are provided in combination therewith in order to supplement the electrical conductivity of display electrodes 11 and 12.
The display electrodes 11, 12 and the bus electrodes 13, 14 are coated with a dielectric substance layer 15, and the dielectric substance layer 15 is coated with a protective film 16 made of magnesium oxide (MgO).
Having a high sputter resistance and a high secondary electron releasing coefficient, the magnesium oxide (MgO) protects the dielectric substance layer 15 for ac operation and functions so as to lower the discharge-starting voltage.
The rear glass substrate 20 has, on the surface confronting the front glass substrate 10, an electrode group consisting of address electrodes 21 making a right angle with the display electrodes 11 and 12 of the front substrate 10, and the address electrodes 21 are coated with dielectric substance layer 22. On the dielectric substance layer 22 separation walls (ribs) 23 are provided partitioning the address electrodes 21 from one another in order to prevent spread of the discharge or to limit the domain of discharge. The ribs 23 are made of a low-melting glass, and they are all the same in interval, height and shape of side wall.
The groove surfaces between the ribs 23 are stripe-wise coated with phosphor layers 24, 25 and 26 each emitting a red-colored, green-colored and blue-colored light, successively. Each of the phosphor layers 24, 25 and 26 is formed by mixing a particulate phosphor with a vehicle to prepare a phosphor paste, forming each paste into stripe-like coatings after forming address electrode 21, dielectric substance layer 22 and rib 23 on the rear glass substrate 20 by the method of screen printing or the like, and thereafter removing the volatile component by baking or the like.
Into the discharge space between the front substrate 10 and the rear substrate 20, a discharge gas such as helium, neon, xenon or the like (not shown in the drawing) is sealed.
In this PDP, a gas discharge is carried out by selecting a discharge cell (unit light emitting area or discharge spot) from one of the display electrodes 11 and 12 (for example, display electrode 12) and the address electrode 21, and repeatedly carrying out gas discharge from the selected discharge cell by a sustaining discharge between the display electrodes 11 and 12.
The gas discharge generates a vacuum ultra-violet light, which excites the phosphor layer of the area to emit a visible light. Thus, a color display can be obtained as a combination of light emissions from the unit light-emitting areas each having the phosphor layers 24, 25 and 26, corresponding to the three primary colors (red, green and blue).
Luminance of color PDPs has been improved year by year, until it has reached about 400 cd/m2 at the present time. However, a color PDP is still lower in luminance than the direct-view type CRT color television of which peak luminance is 600 to 1,000 cd/m2, and a further improvement of the performance of a PDP is urgently needed.
It is an object of the present invention to provide green- and blue-light emitting materials and a phosphor film with which a high-performance PDP can be realized.
It is another object of the present invention to provide a light source having a high-performance fluorescent lamp.
The present invention provides a phosphor capable of emitting a visible light under an exciting light of which main component is ultraviolet light having a wavelength ranging from 100 nm to 400 nm, which is represented by the following composition formula:
(Ba1-a-b-cCaaSrbMc)O.xMgO.yAl2O3 
wherein M is at least one element selected from the group consisting of Eu, Tm, Lu and Mn, and a, b, c, x and y satisfy the following conditions:
0 less than axe2x89xa60.01,
0 less than bxe2x89xa60.01,
0.01xe2x89xa6cxe2x89xa60.3,
0xe2x89xa6xxe2x89xa62.2, and
4.0xe2x89xa6yxe2x89xa612.0.
The present invention further provides a display device and a light source using the above-mentioned phosphor.